1. Field of the Invention
The present invention relates to a cosmetic composition comprising a fruit extract of Chrysophyllum cainito. The present invention also relates to the use of this composition for preventing, for delaying or for combating aging of the skin and/or the appearance of signs of aging of the skin, for example the cutaneous envelope of the breasts. In particular, this composition protects the functionality of the skin cells by inhibiting the glycation of proteins.
2. Description of the Background Art
Glycation is a nonenzymatic process involving a monosaccharide (glucose or ribose), which reacts according to Maillard's reaction with an amine group of an amino acid residue (for example lysine), in particular an amino acid residue of a protein, to form a Schiff base. The latter, after a so-called Amadori molecular rearrangement, can lead, by a succession of reactions, to bridging, in particular intramolecular, for example of the pentosidine type.
This phenomenon is characterized by the appearance of glycation products, the content of which increases regularly as a function of age. The glycation products are for example pyrraline, carboxymethyl-lysine (CML), pentosidine, crossline, Nε-(carboxyethyl)-lysine (CEL), glyoxal-lysine dimer, methylglyoxal-lysine dimer, 3DG-ARG imidazolone, versperlysines A, B, C, threosidine or the end products of advanced glycosylation (or AGEs, for Advanced Glycation End Products).
The glycation of proteins is therefore a universal phenomenon, well known with regard to the skin, particularly its dermal component, and principally in relation to collagen fibers. Glycation of collagen in fact increases regularly with age, leading to a regular increase in the content of glycation products in the skin.
The AGEs constitute a heterogeneous group of structures, whereas the carboxymethyl adducts of lysine (CML) occur most widely in vivo. The CMLs with other AGEs accumulate during the intrinsic aging process leading to stiffening and to a loss of elasticity in tissues such as the skin and vessel walls.
It has long been thought that the AGEs result mainly from reaction between proteins and extracellular glucose. However, recent studies indicate that the intracellular formation of AGEs from dicarbonyl compounds resulting from the autoxidation of glucose greatly exceeds the extracellular formation (Shinohara, M et al. (1998) J. Clin. Investig. 101, 1142-1147). These dicarbonyl compounds are glyoxal, methylglyoxal, and deoxyglucosone 3, which are substrates for reductases. Glyoxal and methylglyoxal are detoxified by the glyoxalase system. The intracellular AGEs induce an oxidizing stress, activate NF-κB and heme oxygenase, and produce products of lipid peroxidation.
A recent study (Thomas Kueper et al. J. Biol. Chem., Vol. 282, Issue 32, 23427-23436, Aug. 10, 2007) identified vimentin, an intermediate filament protein, as the main target of formation of CMLs (carboxymethyl-lysine), in human skin fibroblasts. The intermediate filaments represent one of the major structural elements of the cytoskeleton in addition to actin microfilaments and microtubules. All the intermediate filament proteins have a secondary structure in common, composed of a central helicoidal domain of about 310 amino acids which is flanked by nonalpha helicoidal domains of variable size. Vimentin is required for numerous essential cellular functions such as cellular motility, chemotactic migration, and cicatrization. Modification of vimentin leads to redistribution of vimentin into a perinuclear aggregate. It is clear that the biological impact of the modification of vimentin is associated with loss of contractile capacity of fibroblasts caused by structural breakdown of the intermediate filament system, finally accelerating the aging process.
Thus, nonenzymatic glycation of proteins shows the primary cause of alteration of skin collagen. One of the important consequences of the glycation of proteins is the creation of free radicals. In fact, when they are affected by glycation, proteins react with oxygen and cause the formation of radicals of the superoxide type. The latter are capable of initiating the degradation of proteins, of altering the membrane structures, and finally disorganizing the extracellular matrix and all its components.
Thus, a cosmetic composition containing active substances capable of halting the glycation of proteins can combat skin aging. The appearance of wrinkles and decrease in skin tonicity reflect the aging of the dermis and notably of its mechanical properties.
In particular, in women, the cutaneous envelope of the breasts is particularly sensitive to aging. In fact, the breasts are a pair of organs overlying the pectoral muscles. The mammary gland is constituted of fat lobules and about twenty glandular lobules located deepest in the gland. The fat lobules give the breast its soft consistency and its shape. The glandular lobules have the task of secretion of the milk conveyed by the lactiferous ducts to the lactiferous sinus opening at the nipple. The excretory ducts are surrounded and supported by a framework of connective tissue. The nipple and areola are a point of fixation of the breast but the skin is the principal means of support of the gland. The skin is connected to the superficial fascia of the gland by the Cooper ligaments. The pectoral muscles do not allow the shape to be altered or the breasts to be remodelled.
With age, hormonal influences, variations in weight but also exposure to sunlight, absence of a brassiere etc., the elastic fibers of the skin may break, and the Cooper ligaments may stretch. The skin loses its tonicity, and the breasts sag: this phenomenon is called ptosis. Mammary ptosis reflects a displacement and sagging of the gland and exaggerated distension of the cutaneous envelope. It is therefore necessary to act on this cutaneous envelope by protecting the proteins from glycation, to prevent aging of the breasts.